Shortwave Radiation Balance Research Articles

Quantifying Aspect‐Dependent Snowpack Response to High‐Elevation Wildfire in the Southern Rocky Mountains

AbstractIncreasing wildfire frequency and severity in high‐elevation seasonal snow zones presents a considerable water resource management challenge across the western United States (U.S.). Wildfires can affect snowpack accumulation and melt patterns, altering the quantity and timing of runoff. While prior research has shown that wildfire generally increases snow melt rates and advances snow disappearance dates, uncertainties remain regarding variations across complex terrain and the energy balance between burned and unburned areas. Utilizing paired in situ data sources within the 2020 Cameron Peak burn area on the Front Range of Colorado, U.S., during the 2021–2022 winter, we found no significant difference in peak snow water equivalent (SWE) magnitude between burned and unburned areas. However, the burned south aspect reached peak SWE 22 days earlier than burned north. During the ablation period, burned south melt rates were 71% faster than unburned south melt rates, whereas burned north melt rates were 94% faster than unburned north aspects. Snow disappeared 7–11 days earlier in burned areas than unburned areas. Net energy differences at the burned and unburned weather station sites were seasonally variable, the burned area snowpack lost more net energy during the winter, but gained more net energy during the spring. Increased incoming shortwave radiation at the burned site was 6x more impactful in altering the net shortwave radiation balance than the decline in surface albedo. These findings emphasize the need for post‐wildfire water resource planning that accounts for aspect‐dependent differences in energy and mass balance to accurately predict snowpack storage and runoff timing.

Shortwave radiation balance modulates potential evapotranspiration over China

ABSTRACT Shortwave radiation is an influential driver of global hydrological cycle, as its variation will alter evapotranspiration (ET). While climate change discussion extensively examined ET response to temperature, wind speed and land use/cover variations, little is known about the contribution of shortwave radiation balance on ET partly because of data availability. In this study, we applied the newly-released Global LAnd Surface Satellite (GLASS) products to detect changes in shortwave radiation and albedo for 2003–2018 over China, and quantified their contributions on potential evapotranspiration (PET) which is the upper limit of ET and generally the basis to estimate it. The results showed that downward shortwave radiation declined, together with a slight decrease in albedo, causing a decrease of net shortwave radiation. While climate change affected PET, the decreased net shortwave radiation reduced PET during the period. We identified a hotspot area in the north China plain that is one of the main agricultural production regions, as the radiation balance induced a contrasting effect on PET for the warm and the cold seasons. Our study indicates that it is important to consider shortwave radiation balance when estimating PET and ET to make reliable evaluation of climate change on hydrological cycle and ecosystem response.

Declines in Peak Snow Water Equivalent and Elevated Snowmelt Rates Following the 2020 Cameron Peak Wildfire in Northern Colorado

AbstractWildfires are increasingly impacting high‐elevation forests in the western United States that accumulate seasonal snowpacks, presenting a major disturbance to a critical water reservoir for the region. In the first winter following the 2020 Cameron Peak wildfire in Colorado, the peak snow water equivalent in a high burn severity forest was 17%–25% less than nearby unburned sites. The loss of the forest canopy and a lower surface albedo led to an increasingly positive net shortwave radiation balance in the burned area, resulting in melt rates that were 82%–144% greater than unburned sites and snow disappearance occurred 11–13 days earlier. Late‐season snow storms temporarily buried soot, thus increasing the albedo and delaying melt‐out by an estimated 4 days per storm in our study area. While these storms temporarily reduce the higher melt rates imposed by wildfire impacts, SNOTEL measurements show that they occur non‐uniformly across the western U.S.

Characterizing Warm Temperature during April 2019 Monsoon Transition in the Central part of Java

Warmer temperature than normal has been observed in the central part of Java Island-Indonesia during the monsoon transition in 2019. To explain the environmental process related to temperature variability, this research aims to characterize the process related to temperature anomaly and explain the contributing factors in terms of radiation balance and latent heat flux. This research uses the data from two meteorological stations from the Indonesian Bureau of Meteorology, Climatology, and Geophysics (BMKG) and the National Centers for Environmental Prediction (NCEP/NCAR) Reanalysis Project to explain the temperature anomaly. Several parameters, such as near-surface air temperature and humidity, cloudiness, solar and longwave radiation, as well as latent heat flux are obtained from the reanalysis data. This study focuses on descriptive time-series data analysis to explain the factors that contribute to the April 2019 temperatures. The results of this study show the effect of the Madden–Jullian Oscillation (MJO) on weather anomalies. The increase in humidity when the study area is traversed by the MJO causes an increase in humidity followed by intensive cloud formation and the release of latent heat in the cloud. The release of latent heat contributes significantly to the increase in temperature compared to the effect of the shortwave and longwave radiation balance. Thus, atmospheric phenomena in the tropics need to be studied further concerning warmer temperatures because they can be significantly affected by climate change.

Increasing wildfire impacts on snowpack in the western U.S.

Wildfire area has been increasing in most ecoregions across the western United States, including snow-dominated regions. These fires modify snow accumulation, ablation, and duration, but the sign and magnitude of these impacts can vary substantially between regions. This study compares spatiotemporal patterns of western United States wildfires between ecoregions and snow zones. Results demonstrate significant increases in wildfire area from 1984 to 2020 throughout the West, including the Sierra Nevada, Cascades, Basin and Range, and Northern to Southern Rockies. In the late snow zone, where mean annual snow-free date is in May or later, 70% of ecoregions experienced significant increases in wildfire area since 1984. The distribution of burned area shifted from earlier melt zones to later-melt snow zones in several ecoregions, including the Southern Rockies, where the area burned in the late snow zone during 2020 exceeded the total burned area over the previous 36 y combined. Snow measurements at a large Southern Rockies fire revealed that burning caused lower magnitude and earlier peak snow-water equivalent as well as an 18-24 d estimated advance in snow-free dates. Latitude, a proxy for solar radiation, is a dominant driver of snow-free date, and fire advances snow-free timing through a more-positive net shortwave radiation balance. This loss of snow can reduce both ecosystem water availability and streamflow generation in a region that relies heavily on mountain snowpack for water supply.

The influence of cloudiness and atmospheric circulation on radiation balance and its components

The article contains an analysis of the influence of cloudiness and atmospheric circulation on the components of radiation balance (Q*) using the example of measurements taken in an extra-urban area of Koniczynka near Toruń (Central Poland) in the years 2011–2018. The average annual value of Q* was 1,818.5 MJ·m−2 with a maximum of 352.3 MJ·m−2 in June, and negative values from November to January (December: −27.4 MJ·m−2). The shortwave radiation balance (S*) amounted to 3,129.2 MJ·m−2 and the longwave radiation balance (L*) was ˗1,310.7 MJ·m−2. In June the average solar irradiance (S↓) at midday was 600 W·m−2. The natural annual and diurnal course of Q* components, determined by astronomical factors, is disturbed by changes in cloudiness and inflow of various air masses. It has been found that an increase in cloudiness causes the amount of incoming solar radiation (S↓) to fall, thus decreasing the S* balance. Moreover, clouds restrict longwave radiation balance (L*), in particular, downward atmospheric radiation (L↓) increases. The opposite relationships of S* and L* affect Q* in individual months. The components of Q* are influenced by atmospheric circulation; it has been observed that anticyclonic types, characterised by smaller cloud amounts, favour a greater influx of (S↓) and—at the same time—greater emittance (L↑); however, Q* is then greater than in the case of cyclonic circulation. A statistically significant trend of Q* and its components has not been ascertained. A notable great year-on-year variability of Q*, ranging from 1,640.4 MJ·m−2 (in 2011) to 2,081.6 MJ·m−2 (in 2018), affects the environment. The changes are related to the cloudiness and the frequency of occurrence of different atmospheric circulation types. The role of snow cover is also important as snow reflects solar radiation which leads to the decrease of S* and—as a result—to a negative value of Q* in winter.

Constraining the Surface Flux of Sea Spray Particles From the Southern Ocean

AbstractModeling the shortwave radiation balance over the Southern Ocean region remains a challenge for Earth system models. To investigate whether this is related to the representation of aerosol‐cloud interactions, we compared measurements of the total number concentration of sea spray‐generated particles within the Southern Ocean region to model predictions thereof. Measurements were conducted from a container laboratory aboard the R/V Tangaroa throughout an austral summer voyage to the Ross Sea. We used source‐receptor modeling to calculate the sensitivity of our measurements to upwind surface fluxes. From this approach, we could constrain empirical parameterizations of sea spray surface flux based on surface wind speed and sea surface temperature. A newly tuned parameterization for the flux of sea spray particles based on the near‐surface wind speed is presented. Comparisons to existing model parameterizations revealed that present model parameterizations led to overestimations of sea spray concentrations. In contrast to previous studies, we found that including sea surface temperature as an explanatory variable did not substantially improve model‐measurement agreement. To test whether or not the parameterization may be applicable globally, we conducted a regression analysis using a database of in situ whitecap measurements. We found that the key fitting parameter within this regression agreed well with the parameterization of sea spray flux. Finally, we compared calculations from the best model of surface flux to boundary layer measurements collected onboard an aircraft throughout the Southern Ocean Clouds, Radiation, Aerosol Transport Experimental Study (SOCRATES), finding good agreement overall.

Factors affecting air temperature in Bulgaria

The research period is 1984–2007 and includes data for air temperatures at 20 Bulgarian and Serbian stations. Also, data for four radiation fluxes and cloud fraction were used in the study. Atmospheric circulation is represented by six different circulation patterns and indices. Statistical methods such as principal component analysis, trend analysis, and correlation were employed in order to solve different problems. The main factor that affects air temperature in Bulgaria is solar radiation. Among different radiation fluxes, the most important is Surface Longwave Upward Flux followed by Surface Shortwave Downward Flux and radiation balance. Circulation factors also contribute to the values of air temperature in Bulgaria. The most significant is East Atlantic teleconnection pattern. Local physical geographical conditions such as relief and large water bodies are also important, especially by modeling and modifying the temperature field over Bulgaria. Average annual and most of average monthly air temperatures have increased in the period 1984–2007. The only exceptions are months of September and December. The observed increase in air temperature is due mainly to the increase in Surface Shortwave Downward Flux, which in turn is due to the decrease in cloudiness. The decrease in cloudiness leads to redistribution of radiation fluxes, increasing the net balance in shortwave spectrum and decreasing the net balance in longwave spectrum. The latter suggests a decreasing greenhouse effect in the studied period over the territory of Bulgaria.

Review of the status and mass changes of Himalayan-Karakoram glaciers

ABSTRACTWe present a comprehensive review of the status and changes in glacier length (since the 1850s), area and mass (since the 1960s) along the Himalayan-Karakoram (HK) region and their climate-change context. A quantitative reliability classification of the field-based mass-balance series is developed. Glaciological mass balances agree better with remotely sensed balances when we make an objective, systematic exclusion of likely flawed mass-balance series. The Himalayan mean glaciological mass budget was similar to the global average until 2000, and likely less negative after 2000. Mass wastage in the Himalaya resulted in increasing debris cover, the growth of glacial lakes and possibly decreasing ice velocities. Geodetic measurements indicate nearly balanced mass budgets for Karakoram glaciers since the 1970s, consistent with the unchanged extent of supraglacial debris-cover. Himalayan glaciers seem to be sensitive to precipitation partly through the albedo feedback on the short-wave radiation balance. Melt contributions from HK glaciers should increase until 2050 and then decrease, though a wide range of present-day area and volume estimates propagates large uncertainties in the future runoff. This review reflects an increasing understanding of HK glaciers and highlights the remaining challenges.

Quantifying the missing link between forest albedo and productivity in the boreal zone

Abstract. Albedo and fraction of absorbed photosynthetically active radiation (FAPAR) determine the shortwave radiation balance and productivity of forests. Currently, the physical link between forest albedo and productivity is poorly understood, yet it is crucial for designing optimal forest management strategies for mitigating climate change. We investigated the relationships between boreal forest structure, albedo and FAPAR using a radiative transfer model called Forest Reflectance and Transmittance model FRT and extensive forest inventory data sets ranging from southern boreal forests to the northern tree line in Finland and Alaska (N = 1086 plots). The forests in the study areas vary widely in structure, species composition, and human interference, from intensively managed in Finland to natural growth in Alaska. We show that FAPAR of tree canopies (FAPARCAN) and albedo are tightly linked in boreal coniferous forests, but the relationship is weaker if the forest has broadleaved admixture, or if canopies have low leaf area and the composition of forest floor varies. Furthermore, the functional shape of the relationship between albedo and FAPARCAN depends on the angular distribution of incoming solar irradiance. We also show that forest floor can contribute to over 50 % of albedo or total ecosystem FAPAR. Based on our simulations, forest albedos can vary notably across the biome. Because of larger proportions of broadleaved trees, the studied plots in Alaska had higher albedo (0.141–0.184) than those in Finland (0.136–0.171) even though the albedo of pure coniferous forests was lower in Alaska. Our results reveal that variation in solar angle will need to be accounted for when evaluating climate effects of forest management in different latitudes. Furthermore, increasing the proportion of broadleaved trees in coniferous forests is the most important means of maximizing albedo without compromising productivity: based on our findings the potential of controlling forest density (i.e., basal area) to increase albedo may be limited compared to the effect of favoring broadleaved species.

Forecasting wet-snow avalanche probability in mountainous terrain

Water percolating through the snow cover can lead to wet-snow instability as well as snowmelt runoff. The accurate prediction of spatial patterns of wet-snow in mountainous terrain therefore has practical applications in both back-country avalanche forecasting and hydrology. Recent research has shown that incident radiation plays a dominant role during the first complete wetting of the snow cover. We therefore investigated if large-scale meteorological forecast data, corrected for subgrid topographic influences on the shortwave radiation balance, together with subgrid mean slopes, can be combined to predict large-scale wet-snow avalanche patterns. Required surface albedo was derived from parameterized snow-covered fraction based on terrain parameters and measured flat field snow depths. We derived avalanche probability density functions for daily mean air temperature and incoming shortwave radiation from detailed observations over six winters using time-lapse photography. Based on probability density functions of these meteorological parameters and of slope angles of previous avalanches, we computed wet-snow probability maps for the entire Swiss Alps at a 2.5km resolution. The probability maps compared well with observed wet-snow avalanche activity patterns. Even though the approach cannot forecast the onset of a cycle, since this would require snow cover related parameters, it provides a new approach toward an automatic spatial avalanche forecast built upon simple terrain parameters and easy to obtain large-scale meteorological surface variables. The advantage of our method is that it does not require running small-scale models with demanding model input parameters.

The role of coal pollution in intensification of the fast ice melting in the Sveabukta bay (Van Mijenfjorden, Spitsbergen)

The processes of heat- and mass transfer in Sveabukta Bay sea ice cover during Spring 2010 the particularity of which is conditioned by pollution from open coal storages situated on shore have been studied. Typical features of land fast ice radiation and thermodynamic properties were described and estimates for vertical distribution of coal particles concentration within ice body were obtained. The coal particles were shown to serve as tracers of transfer processes in the sea ice thickness. It was revealed that the integral value of the absorbed solar radiation (shortwave radiation balance) is virtually independent of the features of the incoming solar radiation spectrum and the spectral dependence of the reflectivity of the ice cover of various contaminations. For computation of fast ice evolution characteristics the conceptual thermodynamic model which describes melting processes in the obvious form was used. According to calculations the melt pond forming on dirty ice under typical meteorological conditions begins one – three weeks earlier than that of clear ice depending on degree of contamination characterized by reflective ability of underlying surface. With decreasing of albedo the temperature of melt rises despite the fact that due to time difference the melting of clear ice occurs at higher temperatures.

Snow water equivalent modeling components in NewAge-JGrass

Abstract. This paper presents a package of modified temperature-index-based snow water equivalent models as part of the hydrological modeling system NewAge-JGrass. Three temperature-based snow models are integrated into the NewAge-JGrass modeling system and use many of its components such as those for radiation balance (short wave radiation balance, SWRB), kriging (KRIGING), automatic calibration algorithms (particle swarm optimization) and tests of goodness of fit (NewAge-V), to build suitable modeling solutions (MS). Similarly to all the NewAge-JGrass components, the models can be executed both in raster and in vector mode. The simulation time step can be daily, hourly or sub-hourly, depending on user needs and availability of input data. The MS are applied on the Cache la Poudre River basin (CO, USA) using three test applications. First, daily snow water equivalent is simulated for three different measurement stations for two snow model formulations. Second, hourly snow water equivalent is simulated using all the three different snow model formulae. Finally, a raster mode application is performed to compute snow water equivalent maps for the whole Cache la Poudre Basin.

A comparison of empirical and physically based glacier surface melt models for long-term simulations of glacier response

AbstractWe investigate the performance of five glacier melt models over a multi-decadal period in order to assess their ability to model future glacier response. The models range from a simple degree-day model, based solely on air temperature, to more-sophisticated models, including the full shortwave radiation balance. In addition to the empirical models, the performance of a physically based energy-balance (EB) model is examined. The melt models are coupled to an accumulation and a surface evolution model and applied in a distributed manner to Rhonegletscher, Switzerland, over the period 1929–2012 at hourly resolution. For calibration, seasonal mass-balance measurements (2006–12) are used. Decadal ice volume changes for six periods in the years 1929–2012 serve for model validation. Over the period 2006–12, there are almost no differences in performance between the models, except for EB, which is less consistent with observations, likely due to lack of meteorological in situ data. However, simulations over the long term (1929–2012) reveal that models which include a separate term for shortwave radiation agree best with the observed ice volume changes, indicating that their melt relationships are robust in time and thus suitable for long-term modelling, in contrast to more empirical approaches that are oversensitive to temperature fluctuations.

Formation and Maintenance of Nocturnal Low-Level Stratus over the Southern West African Monsoon Region during AMMA 2006

Abstract The southern parts of West Africa are frequently covered by an extensive deck of shallow, low (200–400 m AGL) stratus or stratocumulus clouds during the summer monsoon. These clouds usually form at night in association with a nocturnal low-level jet (NLLJ) and can persist into the early afternoon hours. Recent work suggests that the stratus deck is unsatisfactorily represented in standard satellite retrievals and state-of-the-art climate models. Here the authors use high-resolution regional simulations with the Weather Research and Forecasting Model (WRF) and observations from the African Monsoon Multidisciplinary Analysis (AMMA) 2006 campaign to investigate (i) the spatiotemporal distribution, (ii) the influence on the shortwave radiation balance, and (iii) the detailed formation and maintenance mechanisms of the stratiform clouds. At least some configurations of WRF satisfactorily reproduce the diurnal cycle of the low-cloud evolution, yielding the following main conclusions: (i) The simulated stratus deck forms after sunset along the coast, spreads inland during the course of the night, and dissipates in the early afternoon. (ii) The average surface net shortwave radiation balance in stratus-dominated regions is about 35 W m−2 lower than in those with fewer clouds. (iii) The cloud formation is related to a subtle balance between “stratogenic” upward (downward) fluxes of latent (sensible) heat caused by shear-driven turbulence below the NLLJ, cold advection, orographic lifting, and radiative cooling on one hand, and “stratolytic” dry advection and latent heating on the other hand.

Seasonal variation in boreal pine forest albedo and effects of canopy snow on forest reflectance

The low shortwave albedo of evergreen coniferous forests increases net radiation and thus the local temperature as compared to open areas. The difference between albedos of evergreen forests and open areas is most pronounced in winter and spring, when the forest canopies mask the reflective ground snow. However, also the albedo of coniferous evergreen forests changes as a function of the amount and optical properties of snow in the ground and canopy. In this study, we examined the shortwave radiation balance of a boreal Scots pine dominated forest. Canopy snow cover was observed to substantially influence the albedo, increasing it by about 0.2 as compared to snow free conditions. However, albedo varied greatly between and within the canopy snow classes, probably due to differences in illumination conditions and snow amount and properties. During midwinter months, most of the incident solar radiation was reflected during days with a lot of snow in the canopy. The difference in reflected radiation between the winters with least and most snow was 54MJm−2, which was also close to the difference (55MJm−2) between the reflectance of an average winter and that of a simulated snow free winter, corresponding to less than 2% of the annual solar irradiance. The albedo of the forest was greatest in midwinter, when the cold weather and low solar radiation caused the falling snow to remain on the tree branches. As the incident solar radiation in these months is very low, we concluded that the positive feedback to climate warming in case of a potentially decreased snow cover in this boreal pine forest would remain small.

Calibration of a physically based, spatially distributed hydrological model in a glacierized basin: On the use of knowledge from glaciometeorological processes to constrain model parameters

In the Dry Andes of central Chile, summer water resources originate mostly from snowmelt and ice melt. We use the physically based, spatially distributed hydrological model TOPKAPI to study the exchange between glaciers and climate in the upper Aconcagua River Basin during the summer season and identify the model parameters that are robust and transferable and those that are more dependent on calibration. TOPKAPI has recently been adapted to incorporate an enhanced temperature index approach for snow and ice melting. We suggest a calibration procedure that allows calibration of parameters in three steps by separating parameters governing distinct processes. We evaluate the parameters' transferability in time and in space by applying the model at two spatial scales. TOPKAPI's ability to simulate the relevant processes is tested against meteorological, ablation, and glacier runoff data measured on Juncal Norte Glacier during two glacier ablation seasons. The model was applied successfully to the climatic setting of the Dry Andes once its parameters were recalibrated. We found a clear distinction between parameters that are stable in time and those that need recalibration. The parameters of the melt model are transferable from one season to the other, while the parameters governing the extrapolation of meteorological input data and the routing of glacier meltwater need recalibration from one season to the other. Sensitivity analysis revealed that the model is most sensitive to the temperature lapse rate governing the extrapolation of air temperature from point measurements to the glacier scale and to the melt parameter that multiplies the shortwave radiation balance.

Shortwave radiation parameterization scheme for subgrid topography

Topography is well known to alter the shortwave radiation balance at the surface. A detailed radiation balance is therefore required in mountainous terrain. In order to maintain the computational performance of large‐scale models while at the same time increasing grid resolutions, subgrid parameterizations are gaining more importance. A complete radiation parameterization scheme for subgrid topography accounting for shading, limited sky view, and terrain reflections is presented. Each radiative flux is parameterized individually as a function of sky view factor, slope and sun elevation angle, and albedo. We validated the parameterization with domain‐averaged values computed from a distributed radiation model which includes a detailed shortwave radiation balance. Furthermore, we quantify the individual topographic impacts on the shortwave radiation balance. Rather than using a limited set of real topographies we used a large ensemble of simulated topographies with a wide range of typical terrain characteristics to study all topographic influences on the radiation balance. To this end slopes and partial derivatives of seven real topographies from Switzerland and the United States were analyzed and Gaussian statistics were found to best approximate real topographies. Parameterized direct beam radiation presented previously compared well with modeled values over the entire range of slope angles. The approximation of multiple, anisotropic terrain reflections with single, isotropic terrain reflections was confirmed as long as domain‐averaged values are considered. The validation of all parameterized radiative fluxes showed that it is indeed not necessary to compute subgrid fluxes in order to account for all topographic influences in large grid sizes.

Net radiation of mountain cultivated Norway spruce (Picea abies (L.) Karst.) stand: evaluation of short- and long-wave radiation ratio

The radiation exchange drives the plant ecosystems energy balance and provides the energy for photosynthesis, transpiration and plant growth. The investigation on net radiation and its component during vegetation season in relation to the clearness index and sun elevation in a cultivated 31-year-old mountain spruce [Picea abies (L.) Karst.] stand is presented. Downward short-wave radiation – S d (incident on the spruce stand was the main part of the short-wave radiation balance during the whole growing season (April–October) 2008. The S d amount is seasonally variable factor determined by the duration of solar shine and the atmosphere transmissivity. Obtained value of net radiation (R n ) and downward short-wave radiation (S d ) ratio amounts to 0.61 on average during the growing season 2008 documenting the importance of the downward short-wave radiation in the net radiation of investigated spruce stand.

Explicit validation of a surface shortwave radiation balance model over snow‐covered complex terrain

A model that computes the surface radiation balance for all sky conditions in complex terrain is presented. The spatial distribution of direct and diffuse sky radiation is determined from observations of incident global radiation, air temperature, and relative humidity at a single measurement location. Incident radiation under cloudless sky is spatially derived from a parameterization of the atmospheric transmittance. Direct and diffuse sky radiation for all sky conditions are obtained by decomposing the measured global radiation value. Spatial incident radiation values under all atmospheric conditions are computed by adjusting the spatial radiation values obtained from the parametric model with the radiation components obtained from the decomposition model at the measurement site. Topographic influences such as shading are accounted for. The radiosity approach is used to compute anisotropic terrain reflected radiation. Validations of the shortwave radiation balance model are presented in detail for a day with cloudless sky. For a day with overcast sky a first validation is presented. Validation of a section of the horizon line as well as of individual radiation components is performed with high‐quality measurements. A new measurement setup was designed to determine terrain reflected radiation. There is good agreement between the measurements and the modeled terrain reflected radiation values as well as with incident radiation values. A comparison of the model with a fully three‐dimensional radiative transfer Monte Carlo model is presented. That validation reveals a good agreement between modeled radiation values.